1. Field of Invention
The present disclosure relates to a fuel heating device of a flex fuel vehicle, and more particularly, to a fuel heating device for improving cold start performance in which in a vehicle using a flex fuel such as ethanol or the like, a temperature of the fuel is increased in a cold start and the increased-temperature fuel is supplied to an engine.
2. Description of Related Art
Today, there is a growing interest in biofuels with backgrounds of high oil prices, energy security, and greenhouse gas emission regulation in international society and the spread of the biofuels is also rapidly progressing.
Among the biofuels, due to the advantages of bioethanol with reduced production costs and significant CO2 emission reduction effect (a reduction of about 40% from gasoline), the use of the bioethanol has been gradually increasing, and production of bioethanol and use of bioethanol as alternative energy are increasing while reducing oil consumption over the globe.
In particular, in Latin American countries including Brazil, the portion of flex fuel vehicles (FFV) is increasing so that the portion of FFV using ethanol as the main fuel is about 75%.
However, a fuel of 100% ethanol has a high ignition point and also has a lower steam pressure of 40 kPa or less than gasoline having a steam pressure of 55-70 kPa, and thus, it may have a start problem in low outer temperature conditions, especially, in the wintertime.
To solve the problems, an auxiliary tank system is used in which a separate fuel for a cold start is stored in an engine room and supplied.
FIG. 1 is a diagram showing a conventional auxiliary tank system 20, in which a fuel supply system using the auxiliary tank system 20 in an FFV using ethanol as a fuel.
The conventional auxiliary tank system 20 is under application to improve low-temperature start performance, and a flex fuel of ethanol and gasoline (for example, a flex fuel containing ethanol of 22% or less) is stored in an auxiliary tank 21 for start improvement, and in a cold start, the flex fuel supplied from the auxiliary tank 21 is supplied to an engine 1.
The auxiliary tank system 20 includes the low-capacity auxiliary tank 21 which stores a cold-start fuel, a dedicated fuel cap 22, a separate fuel pump 23, a bracket 24 for mounting a fuel tank, a fuel line (a cold start line for supplying a fuel to the engine 1 and a vapor line connected with a canister), and a solenoid valve 26 for intercepting or allowing fuel supply through the fuel line.
In the system using the auxiliary tank 21, a controller for controlling fuel supply determines and supplies one of two fuels based on the temperature of cooling water, such that the controller supplies a fuel of the auxiliary tank 21 at a temperature below a set temperature.
To be more specific, when the cooling water temperature is higher than the preset temperature, a fuel pump 11 is driven to supply the fuel of 100% ethanol stored in a main fuel tank 10 to a main injector 2 of the engine 1 through a main line 12; when the cooling water temperature is lower than the preset temperature, the solenoid valve 26 is opened for cold start improvement to supply the fuel stored in the auxiliary tank 21 to a cold start injector (mixer) 26 through a cold start line 25 (fuel pump driving of the auxiliary tank 21).
After a start of the engine 1, the solenoid valve 26 is closed to stop fuel supply from the auxiliary tank 21 and then the fuel of 100% ethanol stored in the main auxiliary tank 10 is supplied to the engine 1 through the main line 12.
However, in such an auxiliary tank system 20, separate parts such as the fuel tank, the fuel cap, the fuel pump, the bracket, and the fuel line needs to be additionally mounted, increasing the cost of the vehicle and increasing the number of parts that are subject to quality assurance and after/service (A/S).
Moreover, there are several problems such as a need for an additional space in a small engine room, a need for injection of a separate fuel, an increase of the fuel cost burden, and a risk of a fire in fuel injection (fuel flow in the engine room).
Generally, in the engine room, the auxiliary tank system 20 is installed close to a dash panel near the indoor, such that in the case of collision, problems, such as damages of a fuel tank and a fuel line (fuel leakage), introduction of the smell of the fuel into the indoor, manipulation problems of the dedicated fuel cap, and excessive pump noise in a start, occur.
To solve the problems, a scheme for heating a fuel supplied from a fuel tank by using a heater in a cold start has been proposed and such a scheme needs heat capacity which may increase the fuel temperature to a set temperature or higher within a short time.
As heater-using schemes, a fuel rail heating system and a fuel injector heating system exist; however, the fuel rail heating system needs a large-capacity heater due to low heat efficiency and necessarily needs preheating, and the fuel injector heating system has low safety (e.g., a back fire).
In addition, a scheme in which a heater is installed in a fuel pump disposed inside a fuel tank, instead of being installed in a fuel rail or an injector, has been proposed, and this scheme adds a heater into a fuel discharge line of the fuel pump in which power is supplied to the heater installed in the fuel pump and the heater is heated to increase the temperature of the fuel discharged from the fuel pump in a start and supply the temperature-increased fuel to the engine.
However, in this scheme, when the fuel heated by the fuel pump is supplied to the engine, the temperature of the fuel is difficult to maintain. In the cold start condition at a sub-zero temperature, a heat loss is large in the fuel line to the engine, so that even when a heat insulating material is put on the fuel line, it is difficult to increase the temperature of a fuel supplied to the engine to a target temperature within a short time of a start instant.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.